In automatic mold making machines, such as the machine described in applicant's U.S. Pat. No. 3,406,738, the mold is formed by compacting a mixture of sand and a binder around a pattern within a mold flask. To compact the sand within the flask, the sand is compressed between a platen and a squeeze head with the pressure being applied by a hydraulic or pneumatic cylinder.
To hold the mold in place on the platen, locking pins have traditionally been used to restrain the mold against lateral movement on the platen. The locking pins are advanced upwardly into the sand prior to the high-pressure squeeze so that the pins protrude into the compacted sand and thereby lock the mold against lateral movement on the platen. When it is subsequently desired to remove the mold, the locking pins are retracted to permit the mold to slide freely over the platen.
These locking pins and their drive mechanisms add to the cost of automatic mold-making machines, and also present problems when sand filters down around the pins and into the drive mechanism. The sand can lead to abrasion problems, which in turn cause wear and maintenance problems throughout the operating life of the machine.